In blood gas analysis, it is important that air and other gaseous materials not be allowed to contaminate the blood as these contaminates distort the results of the gas analysis. Accordingly, prior art syringes adapted to withdraw blood samples from donors are normally preconditioned by the addition of an anticoagulant solution to fill the void or dead space in the syringe and needle, to purge the syringe and needle of air or other gaseous materials and to provide an anticoagulant for the blood. The anticoagulant solution, however, is typically very dilute with the anticoagulant concentration being approximately 1000 units per millileter and the diluent being made up of alcohol, water, and other materials which can also distort the gas analysis of the blood.
Therefore, it is desirable in taking blood samples for blood gas analysis to isolate the blood from extraneous gaseous materials and from the diluent of the anticoagulant solution while leaving the anticoagulant itself to prevent coagulation of the blood.
Accordingly, it is an object of the present invention to provide a new and improved syringe for taking blood samples which prevents contamination by extraneous gases as well as the diluent of anticoagulant solutions.
It is another object of the present invention to provide a syringe for taking blood from a donor wherein the syringe includes a plunger member into which an initial sample of the blood is drawn to purge air and other gaseous materials from the chamber in the syringe thereby preventing the gaseous materials from contaminating the blood sample.